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{{Short description|Principles to describe the practical behavior of colourscolors}}

{{Distinguish|colourimetrycolorimetry}}

{{Other uses}}

{{Use American English|date=August 2016}}

[[File:GoetheFarbkreis.jpg|right|thumb|[[Johann Wolfgang von Goethe]]'s colourcolor wheel from his 1810 ''[[Theory of Colours]]'']]

'''ColourColor theory''', or more specifically '''traditional colourcolor theory''', is a historical body of knowledge describing the behavior of colourscolors, namely in [[colourcolor mixing]], [[colourcolor contrast]] effects, [[colourcolor harmony]], [[colourcolor scheme]]s and [[colourcolor symbolism]].<ref name="Handprint1">{{cite web |last1=MacEvoy |first1=Bruce |title=ColourColor Theory |url=https://handprint.com/HP/WCL/wcolor.html |website=Handprint |access-date=8 February 2024}}</ref> Modern colourcolor theory is generally referred to as [[colourcolor science]]. While there is no clear distinction in scope, traditional colourcolor theory tends to be more subjective and have artistic applications, while colourcolor science tends to be more objective and have functional applications, such as in chemistry, astronomy or [[colourcolor reproduction]]. ColourColor theory dates back at least as far as [[Aristotle]]'s treatise ''[[On ColoursColors]]'' and [[Bharata (sage)|Bharata]]'s [[Natya_Shastra|''Nāṭya Shāstra'']]. A formalisationformalization of "colourcolor theory" began in the 18th century, initially within a partisan controversy over [[Isaac Newton]]'s theory of colourcolor (''[[Opticks]]'', 1704) and the nature of primary colourscolors. By the end of the 19th century, a schism had formed between traditional colourcolor theory and colourcolor science.

== History ==

ColourColor theory is rooted in antiquity, with early musings on colourcolor in [[Aristotle]]'s (d. 322 BCE) ''[[On ColoursColors]]'' and [[Ptolemy]]'s (d. 168 CE) ''[[Optics (Ptolemy)|Optics]]''. The [[Natya_Shastra|''Nāṭya Shāstra'']] (d. 200 BCE) composed in [[Ancient India]], had an early, functional theory of colourcolor,<ref name="Natyashastra">{{cite web |url=https://www.wisdomlib.org/hinduism/book/the-natyashastra/d/doc210153.html |title=Chapter XXIII 'Costumes and Make-up' |last=Shastri |first=Babulal |publisher=Motilal Banarasidass |date=April 16, 2025 |website=Wisdomlib |access-date=April 16, 2025}}</ref> considering four colours as primary, [[black]], [[blue]], [[yellow]] and [[red]]. It also describes the production of derived colourscolors from [[Primary_color|primary colourscolors]].

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The influence of light on colourcolor was investigated and revealed further by [[al-Kindi]] (d. 873) and [[Ibn al-Haytham]] (d. 1039). [[Ibn Sina]] (d. 1037), [[Nasir al-Din al-Tusi]] (d. 1274), and [[Robert Grosseteste]] (d. 1253) discovered that contrary to the teachings of Aristotle, there are multiple colourcolor paths to get from black to white.<ref>{{cite journal |last1=Smithson |first1=H.E. |last2=Dinkova-Bruun |first2=G. |last3=Gasper |first3=G.E.M. |last4=Huxtable |first4=M. |last5=McLeish |first5=T.C.B. |last6=Panti |first6=C.P. |title=A three-dimensional color space from the 13th century |journal=J. Opt. Soc. Am. A |date=2012 |volume=29 |issue=2 |pages=A346–A352 |doi=10.1364/josaa.29.00A346|pmid=22330399 |pmc=3287286 |bibcode=2012JOSAA..29A.346S }}</ref><ref>{{cite journal |last1=Kirchner |first1=E. |title=ColourColor theory and colourcolor order in medieval Islam: A review |journal=ColourColor Research & Application |date=2013 |volume=40 |issue=1 |pages=5–16 |doi=10.1002/col.21861}}</ref> More modern approaches to colourcolor theory principles can be found in the writings of [[Leone Battista Alberti]] (c. 1435) and the notebooks of [[Leonardo da Vinci]] (c. 1490).[[File:Color diagram Charles Hayter.jpg|thumb|Page from 1826 ''A New Practical Treatise on the Three Primitive Colours Assumed as a Perfect System of Rudimentary Information'' by [[Charles Hayter]]]]

[[Isaac Newton]] (d. 1727) worked extensively on colourcolor theory, helping and developing his own theory from stating the fact that white light is composed of a spectrum of colourscolors, and that colourcolor is not intrinsic to objects, but rather arises from the way an object reflects or absorbs different wavelengths. His 1672 paper on the nature of white light and colours forms the basis for all work that followed on colour and colour vision.<ref>{{Citation |last=Marriott |first=F.H.C. |date=2014 |orig-year=1962 (print) |title=Colour Vision: Introduction |url=https://linkinghub.elsevier.com/retrieve/pii/B9781483230894500212 |work=The Visual Process |publisher=Elsevier |pages=219–229 |doi=10.1016/b978-1-4832-3089-4.50021-2 |isbn=978-1-4832-3089-4 |access-date=2025-03-02 |language=en|url-access=subscription }}</ref>

The RYB primary colourscolors became the foundation of 18th-century theories of [[color vision]],{{Citation needed|date=September 2018}} as the fundamental sensory qualities that are blended in the perception of all physical colourscolors, and conversely, in the physical mixture of [[pigment]]s or [[dye]]s. These theories were enhanced by 18th-century investigations of a variety of purely psychological colourcolor effects, in particular the contrast between "complementary" or opposing hues that are produced by colourcolor afterimages and in the contrasting shadows in colouredcolored light. These ideas and many personal colourcolor observations were summarisedsummarized in two founding documents in colourcolor theory: the ''[[Theory of Colours]]'' (1810) by the German poet [[Johann Wolfgang von Goethe]], and ''The Law of Simultaneous Color Contrast'' (1839) by the French industrial chemist [[Michel Eugène Chevreul]]. [[Charles Hayter]] published ''A New Practical Treatise on the Three Primitive Colours Assumed as a Perfect System of Rudimentary Information'' (London 1826), in which he described how all colourscolors could be obtained from just three.

Subsequently, German and English scientists established in the late 19th century that colourcolor perception is best described in terms of a different set of primary colours—redcolors—red, green and blue-violet ([[RGB colourcolor model|RGB]])—modeled through the additive mixture of three monochromatic lights. Subsequent research anchored these primary colourscolors in the differing responses to light by three types of [[Cone cell|colourcolor receptors]] or ''cones'' in the [[retina]] ([[trichromacy]]). On this basis the quantitative description of the colourcolor mixture or colourimetrycolorimetry developed in the early 20th century, along with a series of increasingly sophisticated models of [[colourcolor space]] and colourcolor perception, such as the [[opponent process]] theory.

[[File:Munsell-system.svg|thumb|left|[[Munsell colourcolor system|Munsell]]'s 1905 colourcolor system represents colourscolors using three colourcolor-making attributes, ''value'' (lightness), ''chroma'' (saturation), and ''hue''.]]

Across the same period, industrial chemistry radically expanded the colourcolor range of lightfast synthetic pigments, allowing for substantially improved saturation in colourcolor mixtures of dyes, paints, and inks. It also created the dyes and chemical processes necessary for colourcolor photography. As a result, three-colourcolor printing became aesthetically and economically feasible in mass printed media, and the artists' colourcolor theory was adapted to primary colourscolors most effective in inks or photographic dyes: cyan, magenta, and yellow (CMY). (In printing, dark colourscolors are supplemented by black ink, called "key," to make the [[CMYK]] system; in both printing and photography, white is provided by the colourcolor of the paper.) These CMY primary colourscolors were reconciled with the RGB primaries, and subtractive colourcolor mixing with additive colourcolor mixing, by defining the CMY primaries as substances that ''absorbed'' only one of the retinal primary colourscolors: cyan absorbs only red (−R+G+B), magenta only green (+R−G+B), and yellow only blue-violet (+R+G−B). It is important to add that the CMYK, or process, colourcolor printing is meant as an economical way of producing a wide range of colourscolors for printing, but is deficient in reproducing certain colourscolors, notably orange and slightly deficient in reproducing purples. A wider range of colourscolors can be obtained with the addition of other colourscolors to the printing process, such as in [[Pantone]]'s [[Hexachrome]] printing ink system (six colourscolors), among others.

For much of the 19th century artistic colourcolor theory either lagged behind scientific understanding or was augmented by science books written for the lay public, in particular ''Modern Chromatics'' (1879) by the American physicist [[Ogden Rood]], and early colourcolor atlases developed by [[Albert Munsell]] (''Munsell Book of Color'', 1915, see [[Munsell colourcolor system]]) and [[Wilhelm Ostwald]] (Color Atlas, 1919). Major advances were made in the early 20th century by artists teaching or associated with the German [[Bauhaus]], in particular [[Wassily Kandinsky]], [[Johannes Itten]], [[Faber Birren]] and [[Josef Albers]], whose writings mix speculation with an empirical or demonstration-based study of colourcolor design principles.

== ColourColor mixing ==

{{Main|ColourColor mixing}}

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One of the earliest purposes of colourcolor theory was to establish rules governing the mixing of pigments.

Traditional colourcolor theory was built around "pure" or ideal colourscolors, characterisedcharacterized by different sensory experiences rather than attributes of the physical world. This has led to several inaccuracies in traditional colourcolor theory principles that are not always remedied in modern formulations.<ref>{{Cite web|title=handprint: colourmakingcolormaking attributes|url=https://www.handprint.com/HP/WCL/color6.html|access-date=2021-07-31|website=www.handprint.com}}</ref> Another issue has been the tendency to describe colourcolor effects holistically or categorically, for example as a contrast between "yellow" and "blue" conceived as generic colourscolors instead of the three colourcolor attributes generally considered by colourcolor science: [[hue]], [[colourfulnesscolorfulness]] and [[lightness]]. These confusions are partly historical and arose in scientific uncertainty about colourcolor perception that was not resolved until the late 19th century when artistic notions were already entrenched. They also arise from the attempt to describe the highly contextual and flexible behavior of colourcolor perception in terms of abstract colourcolor sensations that can be generated equivalently by any [[visual media]].{{Citation needed|date=September 2022}}

=== Primary colourscolors ===

{{Main|Primary colourcolor}}

[[File:Color star-en (tertiary names).svg|thumb|Primary, secondary, and tertiary colourscolors of the [[RYB colourcolor model]]]]

ColourColor theory asserts three pure primary colourscolors that can be used to mix all possible colourscolors. These are sometimes considered as red, yellow and blue ([[RYB colourcolor model|RYB]]) or as red, green and blue ([[RGB colourcolor model|RGB]]).{{Citation needed|date=April 2024}} Ostensibly, any failure of specific [[paint]]s or [[ink]]s to match this ideal performance is due to the impurity or imperfection of the colourantscolorants. In contrast, modern colourcolor science does not recogniserecognize universal primary colourscolors (no finite combination of colourscolors can produce all other colourscolors) and only uses primary colourscolors to define a given [[colourcolor space]].<ref name="Handprint1"/> Any three primary colourscolors can mix only a limited range of colourscolors, called a [[gamut]], which is always smaller (contains fewer colourscolors) than the full range of colourscolors humans can perceive.<ref>{{Cite web|title=Traditional and Modern Colour Theory Part 1: Modern Colour Theory|url=http://www.huevaluechroma.com/112.php|access-date=2021-10-15|language=en-AU}}</ref> Primary colourscolors also can't be made from other colourscolors as they are inherently pure and distinct.<ref>{{Cite web|title=3 Basic Primary ColoursColors {{!}} Additive and Subtractive ColourColor Mixing|url=https://www.geeksforgeeks.org/primary-colors/|date=February 28, 2024 |access-date=2025-01-10|language=en-USA}}</ref>

=== Complementary colourscolors ===

{{Main|Complementary colourscolors}}

[[File:Chevreul's RYB chromatic diagram.png|upright=1.35|thumb|[[Michel Eugène Chevreul|Chevreul]]'s 1855 "chromatic diagram" based on the [[RYB colourcolor model]], showing [[complementary colourscolors]] and other relationships]]

For the mixing of colouredcolored light, [[Isaac Newton]]'s [[colourcolor wheel]] is often used to describe complementary colourscolors, which are colourscolors that cancel each other's hue to produce an achromatic (white, gray or black) light mixture. Newton offered as a conjecture that colourscolors exactly opposite one another on the hue circle cancel out each other's hue; this concept was demonstrated more thoroughly in the 19th century. An example of [[complementary colourscolors]] would be magenta and green.{{citation needed|date=April 2024}}

A key assumption in Newton's hue circle was that the "fiery" or maximum saturated hues are located on the outer circumference of the circle, while achromatic white is at the centrecenter. Then the saturation of the mixture of two spectral hues was predicted by the straight line between them; the mixture of three colourscolors was predicted by the "centrecenter of gravity" or centroid of three triangle points, and so on.

According to traditional colourcolor theory based on [[subtractive primary colourcolor]]s and the RYB colourcolor model, yellow mixed with purple, orange mixed with blue, or red mixed with green produces an equivalent greygray and are the painter's complementary colourscolors.

One reason the artist's primary colourscolors work at all is due to the imperfect pigments being used have sloped absorption curves and change colourcolor with concentration. A pigment that is pure red at high concentrations can behave more like magenta at low concentrations. This allows it to make purples that would otherwise be impossible. Likewise, a blue that is ultramarine at high concentrations appears cyan at low concentrations, allowing it to be used to mix green. [[Chromium]] red pigments can appear orange, and then yellow, as the concentration is reduced. It is even possible to mix very low concentrations of the blue mentioned and the chromium red to get a greenish colourcolor. This works much better with oil colourscolors than it does with watercolourswatercolors and dyes.

The old primaries depend on sloped [[Absorption spectroscopy|absorption]] curves and pigment leakages to work, while newer scientifically derived ones depend solely on controlling the amount of absorption in certain parts of the [[spectrum]].

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{{Main|Tint, shade and tone}}

When mixing pigments, a colourcolor is produced which is always darker and lower in chroma, or saturation, than the parent colourscolors. This moves the mixed colourcolor toward a neutral colour—acolor—a greygray or near-black. Lights are made brighter or dimmer by adjusting their brightness, or energy level; in painting, lightness is adjusted through mixture with white, black, or a colourcolor's complement.

It is common among some painters to darken a paint colourcolor by adding black paint—producing colourscolors called ''shades''—or lighten a colourcolor by adding white—producing colourscolors called ''tints''. However, it is not always the best way for representational painting, as an unfortunate result is for colourscolors to also shift in hue. For instance, darkening a colourcolor by adding black can cause colourscolors such as yellows, reds, and oranges, to shift toward the greenish or bluish part of the spectrum. Lightening a colourcolor by adding white can cause a shift towards blue when mixed with reds and oranges. Another practice when darkening a colourcolor is to use its opposite, or complementary, colourcolor (e.g. purplish-red added to yellowish-green) to neutraliseneutralize it without a shift in hue and darken it if the additive colourcolor is darker than the parent colourcolor. When lightening a colourcolor this hue shift can be corrected with the addition of a small amount of an adjacent colourcolor to bring the hue of the mixture back in line with the parent colourcolor (e.g. adding a small amount of orange to a mixture of red and white will correct the tendency of this mixture to shift slightly towards the blue end of the spectrum).

=== Split primary palette ===

The split-primary palette is a colourcolor-wheel model that relies on misconceptions to attempt to explain the unsatisfactory results produced when mixing the traditional primary colourscolors, red, yellow, and blue.

Painters have long considered red, yellow, and blue to be primary colourscolors. In practice, however, some of the mixtures produced from these colourscolors lack [[ColourfulnessColorfulness|chromatic intensity]]. Rather than adopt a [[CMY colourcolor model|more effective set of primary colourscolors]],<ref>{{cite web |last1=Baird |first1=Christopher S. |title=Associate Professor of Physics |url=https://www.wtamu.edu/~cbaird/sq/2015/01/22/why-are-red-yellow-and-blue-the-primary-colors-in-painting-but-computer-screens-use-red-green-and-blue/ |website=Science Questions with Surprising Answers |publisher=West Texas A&M University |access-date=12 June 2024}}</ref> proponents of split-primary theory explain this lack of chroma by the purported presence of impurities, small amounts of other colourscolors in the paints, or biases away from the ideal primary toward one or the other of the adjacent colourscolors. Every red paint, for example, is said to be tainted with, or biased toward, either blue or yellow, every blue paint toward either red or green, and every yellow toward either green or orange. These biases are said to result in mixtures that contain sets of [[complementary colourscolors]], darkening the resulting colourcolor. To obtain vivid mixed colourscolors, according to split-primary theory, it is necessary to employ two primary colourscolors whose biases both fall in the direction, on the colourcolor wheel, of the colourcolor to be mixed, combining, for example, green-biased blue and green-biased yellow to make bright green. Based on this reasoning, proponents of split-primary theory conclude that two versions of each primary colourcolor, often called "cool" and "warm," are needed in order to mix a wide [[gamut]] of high-chroma colourscolors.<ref>{{cite web |last1=Kemp |first1=Will |title=The Hidden Hues of Colour Mixing |url=https://willkempartschool.com/the-hidden-secret-of-colour-mixing/ |website=willkempartschool.com |date=27 August 2011 |publisher=Will Kemp Art School |access-date=15 October 2023}}</ref><ref>{{cite web |last1=Short |first1=Susie |title=Working with a Split Primary Color Palette |url=https://danielsmith.com/artists/insights/susie-short-working-with-a-split-primary-color-palette/ |website=danielsmith.com |date=21 July 2022 |publisher=Daniel Smith |access-date=15 October 2023}}</ref>

In fact, the perceived bias of colourscolors is not due to impurity. Rather, the appearance of any given colourantcolorant is inherent to its chemical and physical properties, and its purity unrelated to whether it conforms to our arbitrary conception of an ideal hue. Moreover, the identity of gamut-optimisingoptimizing primary colourscolors is determined by the physiology of [[Trichromacy|human colourcolor vision]]. Although no set of three primary paints can be mixed to obtain the complete colourcolor gamut perceived by humans, red, yellow, and blue are a poor choice if high-chroma mixtures are desired. This is because painting is a [[subtractive colourcolor]] process, for which red and blue are secondary, not primary, colourscolors.

Although flawed in principle,<ref>{{cite web |last1=Lucariello |first1=Joan |last2=Naff |first2=David |title=How Do I Get My Students Over Their Alternative Conceptions (Misconceptions) for Learning? Applications of Psychological Science to Teaching and Learning modules |url=https://www.apa.org/education-career/k12/misconceptions |website=APA.org |publisher=American Psychological Association |access-date=12 August 2024}}</ref> the split-primary system can be successful in practice, because the recommended blue-biased red and green-biased blue positions are often filled by near approximations of magenta and cyan, respectively, while orange-biased red and violet-biased blue serve as secondary colourscolors, tending to further widen the mixable gamut.

This system is in effect a simplified version of Newton's geometrical rule that colourscolors closer together on the hue circle will produce more vibrant mixtures. A mixture produced from two primary colourscolors, however, will be much more highly saturated than one produced from two secondary colourscolors, even though the pairs are the same distance apart on the hue circle, revealing the limitations of the circular model in the prediction of colourcolor-mixing results. For example, a mixture of magenta and cyan inks or paints will produce vivid blues and violets, whereas a mixture of red and blue inks or paints will produce darkened violets and purples, even though the angular distance separating magenta and cyan is the same as that separating red and blue.

== ColourColor contrast ==

{{See also|colourcolor contrast}}

In [[Michel Eugène Chevreul]]'s 1839 book ''The principles of harmony and contrast of colours'',<ref name=Chevreul>{{cite book |last1=Chevreul |first1=Michel Eugène |title=De la loi du contraste simultané des couleurs |date=1839}}</ref> he introduced the law of colourcolor contrast, stating that colourscolors that appear together (spatially or temporally) will be altered as if mixed with the complementary colourcolor of the other colourcolor, functionally boosting the colourcolor contrast between them. For example, a piece of yellow fabric placed on a blue background will appear tinted orange because orange is the complementary colourcolor to blue. Chevreul formalisedformalized three types of contrast:<ref name=Chevreul/>

* ''simultaneous contrast'', which appears in two colourscolors viewed side by side

* ''successive contrast'', for the [[afterimage]] left on an achromatic background after viewing a colourcolor

* ''mixed contrast'', for the afterimage left on another colourcolor

=== Warm vs. cool colourscolors <span class="anchor" id="Warm vs. cool colours"></span>===

The distinction between "warm" and "cool" colourscolors has been important since at least the late 18th century.<ref>{{cite web|url=http://www.handprint.com/HP/WCL/color12.html |title=color temperature |publisher=handprint |date=2009-04-19 |access-date=2011-06-09}}</ref> The difference (as traced by etymologies in the [[Oxford English Dictionary|''Oxford English Dictionary'']]), seems related to the observed contrast in landscape light, between the "warm" colourscolors associated with daylight or sunset, and the "cool" colourscolors associated with a greygray or overcast day. Warm colourscolors are often said to be hues from red through yellow, browns, and tans included; cool colourscolors are often said to be the hues from blue-green through blue violet, most greysgrays included. There is a historical disagreement about the colourscolors that anchor the polarity, but 19th-century sources put the peak contrast between red-orange and greenish-blue.{{NoteTag|The traditional warm/cool association of a colourcolor is reversed relative to the [[colourcolor temperature]] of a theoretical radiating [[black body]]; the hottest [[star]]s radiate blue (cool) light, and the coolest radiate red (warm) light.}}

ColourColor theory has described perceptual and psychological effects to this contrast. Warm colourscolors are said to advance or appear more active in a painting, while cool colourscolors tend to recede; used in interior design or fashion, warm colourscolors are said to arouse or stimulate the viewer, while cool colourscolors calm and relax.<ref>{{Cite journal|last=Singh|first=Satyendra|date=2006-01-01|title=Impact of colourcolor on marketing|url=https://doi.org/10.1108/00251740610673332|journal=Management Decision|volume=44|issue=6|pages=783–789|doi=10.1108/00251740610673332|issn=0025-1747|url-access=subscription}}</ref> Most of these effects, to the extent they are real, can be attributed to the higher saturation and lighter value of warm pigments in contrast to cool pigments; brown is a dark, unsaturated warm colourcolor that few people think of as visually active or psychologically arousing.

== Color harmony and color schemes ==